MANURE 



217 



monia leads to an increased production of nitrates. This process 

 is accelerated proportionately to a greater extent than is ammoni- 

 fication, as may be seen from Fig. 44. 



Moreover, there is a much 



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closer correlation between in- 

 creased nitrification and in- 

 creased crop yield due to the use 

 of farmyard manure than there 

 is between increased ammonifi- 

 cation and increased yield. This 

 Is what one would expect when 

 it is recalled that it is the nitrates 

 and not the ammonia upon 

 which plants feed. 



Green Manure. — Farm ma- 

 nure can be obtained only vn con- 

 junction with livestock farming, 

 whereas green manure can be 

 produced and used on all farms. 

 In its use there are several prin- 

 ciples which must be borne in 

 mind. 



1. Legumes feed first on the 

 combined nitrogen of the soil 

 and only turn to the atmosphere 

 when the soil supply is insuiB- 

 cient. 



2. Legumes can feed on at- 

 mospheric nitrogen only when 

 properly inoculated. 



3. One ton of alfalfa hay carries fifty pounds of nitrogen, 

 whereas one ton of clover or pea hay carries approximately forty 

 pounds of nitrogen. 



In addition to carrying to the soil the above named quantities 

 of nitrogen, green manures also carry large quantities of organic 

 matter which furnish food for the soil microflora, and during the 



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S7XWS 





Fig. 44.~inustrating the influence 

 of manure on yield of corn and 

 bacterial activities of the soil. 



